Method for Fitting a Seat Sensor Into a Seat Cushion

ABSTRACT

A method for fitting a sensor onto a seat cushion is disclosed, which is specifically suitable for the assembly of a seat sensor onto a seat cushion, wherein the seat cushion comprises a seating surface having a central region, said central region of said seating surface being at least partially delimited by a groove extending from said seating surface into said seat cushion, and wherein said sensor comprises a first sensor portion to be arranged at least partially at a periphery of said central region. The method comprises the steps of providing a mould ( 10 ) for foaming said seat cushion, said mould comprising at least one ridge ( 14 ) designed for forming said groove into said seating surface of said seat cushion; arranging said first sensor portion ( 18 ) in said mould on said at least one ridge ( 14 ), and foaming said seat cushion, thereby integrating at least part of said first sensor ( 18 ) portion into said seat cushion.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for fitting a seat sensor to aseat cushion.

BRIEF DESCRIPTION OF RELATED ART

An automotive vehicle seat generally comprises a foamed seat cushione.g. made of PU foam, which is arranged on a solid backing structure andcovered by a seat trim made of a textile material or of leather. Theseat cushion comprises one or more grooves, which extend from the upperseating surface of the seat cushion into the seat cushion. A seatcushion typically comprises e.g. two lengthwise extending groovesseparating a central seating surface from the side bolsters and one ormore transverse grooves extending between the opposite lengthwisegrooves.

The grooves are typically used as crimping channels for attaching theseat trim to the seat cushion. For this purpose, a metal wire isembedded in the seat cushion so as to extend along the grooves and to beis partially exposed inside the grooves. The seat trim can then beattached to the exposed portions of the metal wire e.g. by means of hookshaped elements.

In the automotive art, it is furthermore well known to use seat sensorsfor detecting one or more parameters relating to a seating conditionwith respect to the vehicle seats. The determined parameters are thenused in the control of secondary restraint systems, driver warningsystems and/or comfort systems. Specific examples of such seat sensorscomprise passenger detection sensors, child seat presence andorientation detection sensors, occupant classification sensors, seatbelt warning sensors, etc.

The passenger presence detectors, the occupant classification sensorsand the seat belt reminder sensors are usually configured as thinfoil-type sensors comprising e.g. a plurality of pressure sensorsinterconnected by flexible strips, which are to be associated to aseating surface of the vehicle seat. Other sensors, such as e.g. thechild seat presence and orientation detection sensors comprise two ormore antenna structures arranged on a thin flexible carrier material.All these sensors are generally configured to be associated to theseating surface of the vehicle seat, normally between the seat cushionand the seat trim.

Depending on the sensor type, the flexible sensor structures have tocover a large area of the seating surface. This means on the other hand,that if a sensor is placed on top of the seat cushion, the sensor or theflexible strips of the sensor respectively have to cross the grooves ofthe seat cushion at different locations. The crossing of the sensorstrips is typically achieved by providing sensor channels extendingtransversely to the grooves from the upper seating surface to the bottomof the grooves. During assembly of the sensor and the seat cushion, thesensor strips are inserted into these sensor channels so as to cross thegrooves at their bottom.

This technique is suitable for seat cushions with shallow grooves and/orseat and sensor configurations which lead to a small number of crossingpoints between sensor strips and crimp channels. If however the seatcushion comprises a high number of transverse crimp channels, which inaddition are very deep, this classical assembly method is renderedvirtually impossible.

Document EP-A-0 785 101 discloses a method for foaming an electricallycontactable functional mat into the seat cushion of a vehicle seat. Inparticular, this document discloses a mould that is provided withpositioning domes arranged in a lower mould portion, which isresponsible for forming the bottom surface of the seat cushion. Thefunctional mat is placed into the mold in such a way that correspondingpositioning recesses of the sensor mat are put on the positioning domesso as to keep the sensor mat in a precise position during the foamingprocess.

BRIEF SUMMARY OF THE INVENTION

The invention provides a different method for assembling a seat sensoron a seat cushion.

The invention further provides a method for fitting a sensor onto a seatcushion.

This method is specifically suitable for the assembly of a seat sensoronto a seat cushion, wherein the seat cushion comprises a seatingsurface having a central region, said central region of said seatingsurface being at least partially delimited by a groove extending fromsaid seating surface into said seat cushion, and wherein said sensorcomprises a first sensor portion to be arranged at least partially at aperiphery of said central region.

In order to overcome the abovementioned problems, the method of thepresent invention comprises the steps of

providing a mould for foaming said seat cushion, said mould comprisingat least one ridge designed for forming said groove into said seatingsurface of said seat cushion;

arranging said first sensor portion in said mould on said at least oneridge, and foaming said seat cushion, thereby integrating at least partof said first sensor portion into said seat cushion.

According to the present invention, the sensor or the first sensorportion is at least partially foamed into the seat cushion instead ofplacing the sensor onto the seating surface. The sensor is integrated ata depth, which substantially corresponds to the depth of the grooves,such that crossings between the sensor strips and the grooves are nolonger critical. The method according to the present inventioneliminates the need for complicated sensor assembly and is thusspecifically suitable for seats having a high number of grooves and/orfor seats where the grooves are very deep.

Furthermore, the seat assembly is radically shortened, as the sensor isalready integrated after the foaming process. This is especiallyimportant in today's just in time delivery conditions. Finally, theintegration of the sensor into the seat cushion foam ensures a reliablepositioning of the sensor during the vehicle lifetime, so that detectionaccuracy is preserved over lifetime.

It will be noted, that the sensor comprises a connection strip, whichenables connection of the sensor to an external evaluation unit. Duringthe arrangement of the sensor into the mould, this connection strip islead out of the mould and arranged so that the extremity carrying theconnection terminals extends outside of the mould. It follows that afterthe foaming of the seat cushion, the connection terminals are accessibleoutside of the cushion for later connection of the sensor to theevaluation unit.

The first sensor portion comprises e.g. an antenna arrangement of achild seat presence and orientation detection (CPOD) system. Such a CPODsystem is e.g. disclosed in EP-A-0 708 002. The antenna arrangementcomprises e.g. one single receiving antenna loop, which has to beassociated to the seating surface so as to substantially surround thecentral portion of the seating surface. The antenna arrangement furthercomprises two emitting antenna loops, each of which should surround onehalf of the central portion.

According to the present invention, the antenna loops are foamed intothe seat cushion at a depth, which corresponds substantially to thedepth of the crimp channels. It follows that the distance between thelengthwise extending grooves no longer limits the dimensions (e.g. thewidth) of the antenna loops. In fact, as the crossing between theantenna loops and the grooves is not critical, the antenna loops may bedimensioned so as to extend beyond the grooves, thus increasing thetotal area of the antenna loops. This increase of the antenna loop areacompensates the decreased detection height of the sensor due to itsarrangement at a certain depth below the seating surface.

In a preferred embodiment of the invention, said step of arranging saidfirst sensor portion in said mould comprises the steps of attachingauxiliary inserts onto said ridge and fastening said first sensorportion onto said auxiliary inserts. The auxiliary inserts may be placedonto the ridges of the mould and after their correct positioning in theseat the sensor may be attached to the auxiliary inserts. Alternatively,the auxiliary inserts may be fastened to the first sensor portion priorto their arrangement into the mould and only subsequently attached attheir respective positions on the mould ridges.

It will be appreciated that the auxiliary inserts should be designed soas to be easily removable from the ridges after the foaming process. Infact, during the foaming, the auxiliary inserts are foamed together withthe first sensor portion into the seat cushion and thus remain a part ofthe seat cushion. It follows, that the auxiliary inserts are removedfrom the mould together with the seat cushion and should accordingly beeasily separable from the ridges.

In a possible embodiment, the auxiliary inserts comprise a base portionand a clip portion extending from said base portion, said clip portionfor removably clipping said auxiliary insert onto an upper edge of saidridge. Such a clipable insert is easily attached to the ridges and thusensures a reliable positioning of the inserts with respect to the ridgesduring foaming. It should be noted that after the foaming process, theclip portion extends from the bottom of the groove along the lateralwalls of the groove. The first sensor portion is preferably attached tothe base portion of the auxiliary insert. The sensor strips may befastened by any suitable means such as e.g. clips, hook and loopfasteners, rivets or the like or by an adhesive.

It will be appreciated, that the sensor strips may be provided withspecific fastening lugs for fastening the sensor to the auxiliaryinserts. These fastening lugs may be positioned asymmetrically on thesensor so as to ensure a correct positioning of the sensor and to avoidthe sensor being arranged upside down.

The auxiliary insert may be a designated part, which is only used totemporarily attach the first sensor portion onto the ridges of themould. In a different embodiment, the auxiliary inserts may serve otherpurposes e.g. to arrange other elements into the mould prior to thefoaming step. The auxiliary inserts may e.g. comprise trim hooks, whichare integrated into the seat cushion foam for later attachment of theseat trim. Alternatively said auxiliary inserts are adapted to positiona metal wire into said mould, said metal wire extending along said ridgefor being at least partially foamed into said cushion. The metal wirepartially foamed into the cushion can then serve for attaching a seatupholstery or seat trim after the foaming of the cushion.

Depending on the application, the seat sensor may comprise a secondsensor portion to be arranged on top of said seating surface of saidseat cushion. This is e.g. the case for seat belt reminder seat sensors,which are arranged in the rear area of the seating surface for detectingthe presence of a passenger on the seat. The seat belt reminder sensorcomprises several pressure sensitive cells, which should be arrangedbetween the seat cushion and the seat trim. In this case, the method maycomprise the further step of inserting said second sensor portion into asecondary cavity within said mould.

The secondary cavity is e.g. arranged in the mould portion forming theupper seating surface of the seat cushion, e.g. the bottom of the mould,as the foam cushions are traditionally foamed upside down. Afterinsertion of the second sensor portion, the secondary cavity ispreferably closed (towards the main mould cavity) by means of a cover,so that during the foaming process, a penetration of the foam materialinto the secondary cavity is prevented. After the foaming process, thesecond sensor portion is removed from the cavity and remains freelyaccessible above the seating surface.

The second sensor portion also comprises a connection strip enabling thesecond sensor portion to be connected to an evaluation unit. Thearrangement of the second sensor in the mould is preferably such thatthe connection strip of the second sensor portion extends from thesecondary cavity through the main mould cavity to the location, at whichthe connection strip of the first sensor portion is lead out of themould. Both connection strips are accordingly lead out of the mould atthe same location, thus enabling the connection of the different sensorportions at the same location. In a preferred embodiment of the sensor,said first sensor portion and said second sensor portion are furthermoreconnected to a common connection terminal by means of their flexibleconnection strips, thus enabling connection of the different sensorelements by means of a single connector. The common terminal alsoensures a correct positioning of the second seat portion once the firstsensor portion is correctly positioned, thus preventing the secondsensor portion being arranged upside down.

It will be noted, that the connection strip of the second sensor portionis foamed into the seat cushion, thus ensuring a reliable positioning ofthe second sensor portion with respect to the seating surface of theseat cushion. The second sensor portion is finally attached to theseating surface by the trim material. It will be noted, that thisembodiment of the present method enables a reliable positioning of thesecond sensor portion by foaming, without subjecting the second sensorportion itself to the foaming process conditions, e.g. as hightemperature or the like. In fact, during the foaming process the secondsensor portion is shielded from the foam by means of the secondarycavity cover, so that no alteration of the sensor characteristic bytemperature may occur. It remains to be noted, that the second sensorportion may further be protected by insertion into a felt pocket or thelike prior to its insertion into the secondary cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more apparent from the followingdescription of several not limiting embodiments with reference to theattached drawings, wherein

FIG. 1: shows a schematic representation of an interior of a mouldportion for foaming a cushion seat,

FIG. 2: an elevation view of an auxiliary insert for attaching thesensor onto the mould ridges;

FIG. 3: a section view of the sensor being fastened to the auxiliaryinsert;

FIG. 4: a section view of the mould after the insertion of the first andsecond sensor portion;

FIG. 5: a view of a combined sensor.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a part of a mould interior 10 for foaming a seat cushion.FIG. 1 only shows the inner parts of the mould, the outline of the mouldbeing indicated by the dashed line 12. The shown mould portion 10comprises several shaping ribs or ridges 14, which extend upwardly fromthe mould bottom for forming grooves into the foamed cushion. The ridges14 are arranged in a specific arrangement, which is given by the designof the seat cushion and the requirements for attaching a seat trim tothe cushion. In the shown embodiment, the ridges are arranged so as toform two lengthwise extending grooves and 4 transverse grooves extendingbetween the two lengthwise grooves.

According to the present invention, a (partially shown) seat sensor 16comprising several flexible sensor strips 18 has to be associated to theseat cushion. This is achieved by arranging the seat sensor in the mouldprior to the foaming of the seat cushion. The sensor is preferablyarranged on the ridges 14, so that after foaming, the sensor is at leastpartially integrated into the seat foam.

The correct arrangement and the positioning of the sensor 16 is achievedby means of auxiliary inserts 20, which are clipped onto the upper edges22 of the ridges 14. The auxiliary inserts may comprise a base portion24 and a clip portion 26 extending from said base portion 24, said clipportion being adapted to be clipped onto the ridges 14 (see FIG. 2). Theauxiliary inserts may be specifically designed for the only purpose offastening the sensor 16 to the ridges. Preferably however, the auxiliaryinserts also serve for attaching the seat trim after the foaming processand/or for positioning an attachment wire inside the mould as describedabove.

The sensor 16 is preferably fastened to the lower surface of theauxiliary insert (see FIG. 3), i.e. to the surface opposite of the clipmeans, which during the upside down foaming process, is directedupwardly. The sensor may be fastened by any suitable means such asclips, hook and loop fasteners, rivets or the like or by an adhesive. Inthe shown embodiment, the sensor is attached by resilient pegs 28, whichextend through respective fixation openings 30 and 32 of the sensor andthe base plate of the auxiliary inserts 20. As can be seen in FIGS. 1and 5, the fixation openings 30 of the sensor are preferably arranged infastening lugs 34, which extend laterally from the sensor strips 18.These fastening lugs 34 may be positioned asymmetrically on the sensor16 so as to ensure a correct positioning of the sensor and to avoid thesensor e.g. being arranged upside down.

FIG. 4 shows a cross-section of a mould 40, 42 after closing and priorto the injection of the foam material. A two-part sensor 116 having afirst sensor portion 118 and a second sensor portion 120 is arranged inthe mould. The first sensor portion 118 is positioned inside the mould40 as described above.

The first sensor portion comprises several flexible sensor strips 118and a connection strip 122 connecting the first sensor portion 118 to aconnection terminal 124. During arrangement of the first sensor portion118 in the mould, the connection strip 122 is arranged so as to lead outof the mould e.g. on the rear side of the seat cushion. It follows thatthe connection terminal 124 is arranged outside the mould and isaccordingly accessible after the foaming process for connection of thesensor to a non shown evaluation unit.

The second sensor portion 120, e.g. a seat belt reminder sensor whichhas to be arranged on the seating surface of the cushion, is alsoarranged inside the mould 40, 42. The second sensor portion 120comprises e.g. a plurality of pressure sensitive cells 126 arranged onflexible sensor strips 128. In order to ensure that second sensorportion 120 is correctly positioned on the upper seating surface, thesecond sensor portion 120 is inserted into a secondary cavity 130, whichis arranged in the bottom of mould portion 40. After the insertion ofthe second sensor portion 120, the secondary cavity 130 may be closedtowards the main mould cavity by means of a cavity cover 132, so thatduring the foaming process, no foam material enters the cavity 130.

The second sensor portion 120 also comprises a connection strip 134connecting the second sensor portion 120 to the connection terminal 124.As shown in FIG. 4, the arrangement of the second sensor portion 120 inthe mould is preferably such that the connection strip 134 of the secondsensor portion 120 extends from the secondary cavity 130 through themain mould cavity to the location, at which the connection strip 122 ofthe first sensor portion 118 is lead out of the mould. It will be noted,that the connection strip 134 will be specifically dimensioned so as toallow the arrangement of the second sensor portion 120 in a plane, whichis distant from the first sensor portion plane.

1. A method for fitting a sensor onto a seat cushion, wherein said seatcushion comprises a seating surface having a central region, saidcentral region of said seating surface being at least partiallydelimited by a groove extending from said seating surface into said seatcushion, and wherein said sensor comprises a first sensor portion to bearranged at least partially at a periphery of said central region, themethod comprising providing a mould for foaming said seat cushion, saidmould comprising at least one ridge designed for forming said grooveinto said seating surface of said seat cushion; arranging said firstsensor portion in said mould on said at least one ridge, and foamingsaid seat cushion, thereby integrating at least part of said firstsensor portion into said seat cushion.
 2. A method according to claim 1,wherein said arranging said first sensor portion in said mould comprisesattaching auxiliary inserts onto said ridge and fastening said firstsensor portion onto said auxiliary inserts.
 3. A method according toclaim 2, wherein said auxiliary inserts comprise a base portion and aclip portion extending from said base portion, said clip portion forclipping said auxiliary insert onto an upper edge of said ridge.
 4. Amethod according to claim 3, wherein said clip portion of said auxiliaryinsert is adapted for attaching a seat trim.
 5. A method according toclaim 2, wherein said auxiliary inserts are adapted to position a metalwire into said mould, said metal wire extending along said ridge forbeing at least partially foamed into said cushion.
 6. A method accordingto claim 1, wherein said sensor further comprises a second sensorportion to be arranged on top of said seating surface of said seatcushion, said method further comprising inserting said second sensorportion into a cavity within said mould.
 7. A method according to claim6, wherein said first sensor portion and said second sensor portion areconnected to a common connection terminal by means of flexibleconnection strips.